step-by-step guide to conducting an i-tree canopy study€¦ · there are four steps to conducting...

January 2019

Forest Research – Urban Forestry Research Group Contact : [email protected]

Step-by-step guide to conducting an i-Tree Canopy study

Contents What is canopy cover? ............................................................................................................................ 1

Want to know the tree canopy cover of your local neighbourhood, ward, town or city? ..................... 1

How i-Tree Canopy works: ...................................................................................................................... 2

Step 1 – Define your study area .............................................................................................................. 3

Step 2 – Set up the study design ............................................................................................................. 5

Step 3 – Conduct the canopy cover assessment ..................................................................................... 8

Step 4 – Save and export your canopy assessment .............................................................................. 11

Step 5 – Share your results ................................................................................................................... 12

Privacy policy ........................................................................................................................................ 13

Step 7 – Reviewing and exporting results ............................................................................................. 14

Acknowledgements ............................................................................................................................... 14

‘Tree’ or ‘non-Tree’ : a picture guide .................................................................................................... 15

UK Ward Canopy Cover Web Map: How to use.................................................................................... 17

What is canopy cover?

Canopy cover is the area of ground in a study area which is covered by tree canopy, often provided

as a percentage.

The amount of canopy cover in an area is linked to the provision of benefits from trees, such as

providing shade, shelter, removing pollutants and carbon dioxide from the air, providing habitat for

wildlife, and making our urban areas more attractive, sustainable and healthy places to be.

Estimating canopy cover across urban areas provides an indicator of the spread of these benefits

across our towns and cities.

Want to know the tree canopy cover of your local neighbourhood,

ward, town or city? i-Tree Canopy https://canopy.itreetools.org/ allows you to estimate tree canopy for any geographic

location. This online tool is free-to-use, quick, and easy too. A canopy assessment for one local

authority ‘ward’ takes only around 45 minutes to complete. People around the world use the tool.

In the UK it was recently used to assess canopy cover of 283 English towns and cities. The results

estimated that the average cover was 15.8%. For details see:

https://www.researchgate.net/publication/322337570_The_Canopy_Cover_of_England%27s_Town

mailto:[email protected]

https://canopy.itreetools.org/

https://www.researchgate.net/publication/322337570_The_Canopy_Cover_of_England%27s_Towns_and_Cities_baselining_and_setting_targets_to_improve_human_health_and_well-being

January 2019


s_and_Cities_baselining_and_setting_targets_to_improve_human_health_and_well-being (or visit

http://www.urbantreecover.org/comparison-table/)

If your town or city isn’t included in this study, or if you want to find out the canopy cover in a

different area or at a finer-scale, use i-Tree Canopy.

We hope to build a ward-level canopy cover map for the UK. Ward level assessments are useful as

they identify the distribution of canopy cover within large towns and cities, so can help identify

priority areas for new tree planting. As an established administrative boundary, canopy cover

assessments can be repeated using the same boundaries and be understood in comparison to other

metrics collected at the ward level. (The source of our ward boundaries is here.)

We developed an online web-map to store and present the findings of this project. This web map

will show selected urban wards for the UK and whether they have had a canopy cover assessment

conducted or not. For wards with canopy cover, the map will show their relative percentage canopy

cover. As more canopy cover assessments are completed this will build up show the distribution of

canopy cover across our urban areas. For a quick overview of the map and what it does, jump to

here.

We hope to you can help us to fill in this canopy cover map by conducting canopy cover assessments

and sending us in your results.

This guide shows you step by step how to do a canopy cover assessment using i-Tree Canopy.

How i-Tree Canopy works: The tool works within a web browser. It creates a set of random points which you then check

through one-by-one deciding if they fall on the canopy of a tree, or not. By comparing the proportion

of points identified as ‘tree’ to ‘non-tree’ we get an estimate of the percentage canopy cover. The

accuracy of this approach improves with the number of random points checked. We recommend at

least 300 points for a ward area. This may sound like a lot! But most points only take a few seconds

to do.

The hardest part in this process is deciding whether a random point has fallen on a tree or a shrub.

To make estimates of canopy cover comparable between different sites and projects, we’re only

interested in canopies that belong to trees. While on the ground a tree may look quite different to a

shrub, viewed from above (as they are in i-Tree Canopy) they can look very similar. Once you get to

the step of identifying canopy forms – see below – we’ll provide more guidance.

There are four steps to conducting an i-Tree Canopy assessment:

1) Defining your study area

2) Set up the study design

3) Conduct the canopy cover assessment, point-by-point

4) Save and export your canopy assessment

We provide further detail on what to do in each Step below.


https://www.researchgate.net/publication/322337570_The_Canopy_Cover_of_England%27s_Towns_and_Cities_baselining_and_setting_targets_to_improve_human_health_and_well-being

http://www.urbantreecover.org/comparison-table/

http://geoportal.statistics.gov.uk/datasets/wards-december-2018-full-clipped-boundaries-uk

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Step 1 – Define your study area You can conduct an i-Tree Canopy study for pretty much any geographic area. A study at ward-level

is meaningful, if you can do all of the wards in your town or city.

You can decide the boundary for your desired study area in three ways: using A, B or C, below:

A. Visit our web map to view wards missing canopy cover and download the ward boundaries

from this site.

i) visit the web map at

http://forestry.maps.arcgis.com/apps/webappviewer/index.html?id=d8c253ab17e1412586d

9774d1a09fa07

Here selected urban wards are visible for the UK. Wards in dark blue are in need of canopy

assessment. Wards in green have been assessed and display their canopy cover estimate.

Wards in yellow have been ‘assigned’ to someone, meaning someone has already

downloaded the shapefile for the ward boundary to conduct a canopy assessment.

ii) Navigate to the ward you’d like to complete.

iii) Click the box at the top of the map. This will open first with an instruction box.

Now click the ward you’d like to complete a canopy assessment for. This should now change

the instruction box to a box with information for your selected ward.

iv) Edit two of the fields in this box to help us keep track of progress and help other

volunteers see which wards are already being worked on. Find the ‘Status’ field and

underneath change the text from “Unassigned” to “Assigned” (case sensitive). Then further

down the box find ‘AssignDate’ and click the box below this heading to select today’s date

from the calendar.

v) Finally, download your boundaries of this ward to complete the canopy cover assessment.

At the bottom of the box, look for the ‘Attachments’ heading. Underneath this should be a

.shp file. Click this to download it. When a pop-up opens click ‘save as’ and save it in a

normal folder somewhere you’ll be able to find later. Do not try to open the file, it will only

open successfully when you upload it to i-Tree Canopy as described in step vi).

Please start with one ward. Once that is done you can assign the next one to you.

Note: To prevent there being many ‘assigned’ wards which have stopped being worked on, if

we don’t hear from you with the results from your ‘Assigned’ ward within a month of the

AssignDate, we will return this ward to ‘Unassigned’. If you’re still working on your ward and

still like time to complete it, please still email us your intention to keep going and send in

your results when you’re done.


http://forestry.maps.arcgis.com/apps/webappviewer/index.html?id=d8c253ab17e1412586d9774d1a09fa07


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vi) Go to https://canopy. itreetools.org/ and click the button ‘load ESRI Shapefile’. Upload

the .shp file you have just downloaded.

vii) Once uploaded the page will refresh and you should now see your boundary outlined in

red on a Google map, to the left-hand side of the screen. Proceed to Step 2.

B. Contact us to get the official ward boundaries. We’ll email you a file (an ESRI GIS shape-file)

that you can then load into i-Tree Canopy. You do not need to have the specialist ESRI software

yourself for this to work! To take this approach:

i) Contact us stating which ward or wards you’d like to estimate canopy cover for (please

include the town or city name as well as the ward name).

We’ll email you each ward as a separate GIS shape-file (a .shp file). Save it to a location

that you’ll remember and can find easily. You are now ready to start your study…

ii) Go to https://canopy.itreetools.org/ and click the button ‘load ESRI Shapefile’. Upload

the .shp file for the ward you want to assess, from the location you selected in the previous

step.

iii) Once uploaded the page will refresh and you should now see your boundary outlined in

red on a Google map, to the left-hand side of the screen. Proceed to Step 2.

Click here to open the editor tool,

then click the ward you’d like to

download.

Click here to select

today’s date

Change the status to from

‘Unassigned’ to ‘Assigned’

Now click here to

download the .shp file to

your computer.




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C. Draw your own bespoke boundaries around your area of interest. This is useful if you’re

interested to find out the canopy cover of more informally defined areas like a park or

neighbourhood. To create an area using this approach, follow these steps:

i) Go to https://canopy.itreetools.org/ and click the button ‘Define Project Area’.

ii) Zoom in or search for your local area. When you’ve found the area you want to define

for your canopy cover assessment, click the blue ‘polygon’ shape button to the top left

of the map.

iii) To start drawing your ‘polygon’, click on the map. This will add your first boundary

point. Keep clicking around your area of interest, to outline the boundary. To finish

drawing, click back on the first point which completes the polygon. Now click the ‘Finish’,

button on the bottom right corner. Proceed to Step 2.

Step 2 – Set up the study design Once you’ve defined your study boundary, you can click the button ‘Configure and Begin Your

Survey’.

The two cover classes of ‘Tree’ and ‘Non-Tree’ show in the table. These classes are what your

random points will be identified as, either ‘Tree’ or ‘Non-Tree’.

Make a quick edit to make the study quicker. If you have ‘Non Tree’ listed above ‘Tree’ in the table,

‘Non Tree’ will be the default option for your random points which makes classifying points faster (as

most random points will not be a tree).

There are two options to change this:

1. Go to our website and download our template configuration file. You can download it at the

bottom of the webpage under ‘downloads’. Save the configuration file to somewhere you’ll be able

to find, then return to the i-Tree Canopy page. Click the ‘Load’ button and select the downloaded

configuration file.

2. Edit the template manually. To change this, click + (Add a new row) below ‘Non-Tree’ and copy

into this new row the same details from the ‘Tree’ row.



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Now delete the top row for ‘Tree’ so that you’re back to two rows only.

Your table should now look like the one below:

Click ‘Next’ here to move on.

The next screen allows you change some settings about the project. Under ‘Select Project Locations”

untick ‘United States of America’. Locations are only set up for the USA and there’s no option (yet) to

select the UK.

In the ‘Benefit Options’ box, tick the box ‘T-Tree’. Within the ‘Currency box’ change the

‘Denomination’ to ‘GBP’ and ‘symbol’ to ‘£’. Below this in the Measurement box change the ‘Units’

to ‘Metric’. This updates the values estimated for benefits associated with tree canopy cover in the

box below. It should look like the screenshot below:


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Then click the ‘Begin Survey’ button (bottom right).


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Step 3 – Conduct the canopy cover assessment This page is where the fun starts and the results start coming up. On the left of your screen you have

the map of your area with the red line boundary shown (no points are shown yet).

To the right of the map is a graph which will update as you go through identifying the random

points. It will give you the percentage of points identified as ‘Tree’ (T) or ‘Non Tree’ (NT). It will also

give you a measure of the accuracy of these two percentages, known as the standard error. The

more points you complete, the more accurate your estimated canopy cover, and the smaller your

standard error value will be.

Below the graph is a table with the heading shown of Id, Cover Class, Latitude, Longitude.

To get started click the ‘+’ under Id. This will add your first assessment point to the aerial view map.

The map on the right will zoom into an area approximately 80 * 80m with the assessment point as

yellow cross-bars in the centre of the map.


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You can zoom in and out of the map and move around to get a better feel for the picture and the

surroundings, including canopy cover. You may also wish to increase the zoom of your internet

browser, so that you see the relevant part of your browser more clearly.

For the assessment, the question is not whether there are any trees in the full aerial view at all,

but if the yellow cross bar is directly on a tree.

What’s a tree? We are interested in Tree Canopy Cover, not shrub cover - though it can be difficult to tell the difference when viewed from above. Here are some guiding principles to help you tell a tree from a shrub: If it’s an ornamental type tree in a garden (like a cherry) yes it’s a tree If it’s a garden hedge, no - it’s not a tree If it’s a hedgerow along a road, assess scale by zooming in and out of the map – if it looks like a

tree, select tree, but if it looks small and scrubby select non-tree If the cross is on the shadow from a tree, it’s not a tree! If it’s a map of waste land, again assess scale by zooming in and out. Try to determine whether it

is a tree, or merely a shrub or other vegetation. Throughout, the trick is to be consistent please Some example images are provided at the end of this document.


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Once you’ve decided whether the point is on a tree or not, select the appropriate value:

Change the value of the drop down menu to “Tree” or just accept the default ‘Non-Tree’. Click the

‘+’ button to add the next random point.

If you want to go back to another point to check it and/or change it, click that point’s row in the

table. You can now change between ‘Tree’ / ‘Non Tree’ once again in the drop-down menu.

Once you have your eye-in you’ll speed up. About 50 points in 5-8 minutes, or 500 in an hour. You

can take a break by saving your data at any time, and coming back to it later.

To save your data, click the ‘Save your Data’ button.

You’ll see lower down the page the option to ‘Save your Data’. Do this for approximately every 50

points, in case the web crashes and you need to reload. Click the ‘Save Data’ button underneath the

table. Save it as a .dat file in a location that you will remember (in many browsers the default will be

your ‘Downloads’ folder). This file can be re-uploaded into i-Tree Canopy so you can check your

results or continue working on it. We’ll also ask you later to email it to us.


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The number of points to assess depends on the size of the area you are assessing. For a ward we

recommend a minimum of 300. For large wards or larger areas closer to 500 may be needed. If you

are doing a large town or city, you will need more points than 500. For example, in the past we’ve

used 3,000 random points to assess canopy cover for Greater London.

For ward assessments, we suggest aiming for 300 points, then check the standard error value. If the

standard error is more than 2%, you could continue adding points to try to reduce this to less than

2% standard error.. If you are doing multiple wards in one town or city, we recommend you try to do

the same minimum number of assessment points in each ward.

Step 4 – Save and export your canopy assessment At the end of the survey, click the ‘Save Data’ button underneath the table to make the final save of

the data as a .dat file. In most cases, this file will be in your downloads folder, but please check. If

you saved the data multiple times (every 50 assessment points - as back-up), make sure you pick the

most recent file at the end:

To have results which you can look at in an MS Excel file, you can also click the ‘Export’ button

(above the google map). This will export the results as a .csv file, which you can then open in MS

Excel or Open Office. This file will include point Id, the cover class assigned for each point, the

description of each cover class, and the latitude and longitude coordinates for each point.

You can also view a report of your canopy cover assessment by clicking the ‘Report’ button above

the map. This will show you the graph of canopy cover and error estimates, the data in a table and

the estimated tree benefits for the estimated canopy cover. You can print this report or save it as a

jpeg or pdf.


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To finish the project, click the Exit button (above map on the right). The next screen gives you another option to save your data as a .dat file in case you forgot before leaving the last page. You can start assessing another area by clicking ‘Start New Project’ which takes you back to the beginning…but before you start again… Take a break from the screen to rest your eyes! We recommend you take a 5 minute break every 20 minutes, and a 15 minute break after one hour.

Step 5 – Share your results Please send us your results!

This information can help us better understand levels of tree canopy cover across the country. We

can add your findings to our ward canopy cover map for the UK to help fill in the distribution of

canopy cover in the UK.

To send us your results:


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1. Email us at: [email protected]

2. Please remember to tell us all of the following

information:

Name of Ward:

% Estimate canopy cover:

Standard error:

Number of random points checked:

3. Please also attach the .dat file for each ward.

4. In sending them to us we will assume that you are happy for us to share these on the

website, where it will be visible and downloadable.

5. Let us know if you’d like yourself or your organisation who collected the data would like to

be acknowledged for the assessment for each ward. We can add your name and /

organisation as well as a link to your organisations webpage or further information about

the canopy assessment. Please be aware, this information will be open and downloadable by

others.

6. We will retain your email while we process the data in case we need to contact you

regarding any queries. Subsequently we will delete your contact information.

If you would like to receive updates on the project, please confirm by email. In this case we

will retain your contact information.

Privacy policy The Forestry Commission’s Personal Information Charter can be found here: https://www.gov.uk/government/organisations/forestry-commission/about/personal-information-charter. Any information we collect from you will be managed according to this policy and is subject to data protection. This policy complies with the General Data Protection Regulation (EU 2016/679) introduced on 25 May 2018. Contact information provided via this ward canopy cover website will be held by Forest Research for a reasonable limited period while the canopy cover data supplied is processed, after that it will be deleted accordingly. I understand that this information will be held securely in the UK or EU by Forest Research (Forestry Commission) and will not be used for any other purpose. The Forestry Commission is registered as a data controller under the Data Protection Act 1998 (Registration No: Z6542658).



https://www.gov.uk/government/organisations/forestry-commission/about/personal-information-charter

https://www.gov.uk/government/organisations/forestry-commission/about/personal-information-charter

https://gdpr-info.eu/

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Step 7 – Reviewing and exporting results We want this data to be fully available to all to support urban tree awareness, research,

stewardship and management. The data can be selected to review statistics for a certain area. This

selected data can then also be downloaded in various formats. If you want a large section of data

difficult to select through the online map, get in touch with us and we’d be happy to extract the data

and send it to you.

Acknowledgements This guide was written by Kathryn Hand and Kieron Doick, Forest Research. We are grateful to Dr

Ingo Schüder, Director Brillianto, for road-testing and improving the guidance and for providing

additional screen-shots for the step-by step instructions


https://www.forestresearch.gov.uk/

https://www.brillianto.biz/

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‘Tree’ or ‘non-Tree’ : a picture guide Example Tree or

non-Tree? Description

TREE Cross-bars fall onto the canopy of a small tree. The fact that it casts a sizeable shadow and covers the fence-line helps identify it as a tree, rather than a shrub.

TREE The yellow cross-bars fall on top of a tree. Aerial photographs are often taken in winter, so often the trees are bare and brown rather than leafy and green. However here you can see the tree’s branches reaching out and see the cross-bars fall on the canopy area of those branches.


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NON-TREE The yellow cross-bars fall just on the side of a formally cut hedge, which counts as a shrub rather than a tree.

NON-TREE The yellow cross-bars fall on the shadow from a cluster of trees, rather than on the tree itself, therefore is classed as non-tree.


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UK Ward Canopy Cover Web Map: How to use Access the online interactive web map here. This web map shows urban wards from across the UK. The web map allows you to both view the results of canopy assessments and the progress of this project, but also to download ward boundaries so you can get started on your canopy cover assessment. Why wards? Wards are administrative boundaries and are useful to define smaller areas within towns and cities to investigate canopy cover at a more detailed level. However, administrative wards do not always capture urban boundaries well, and particularly rural towns may not be included as their ward boundaries cover large rural areas which would give a poor estimate of urban canopy cover. If your urban area is missing from the map please get in touch with us and we’ll try to source an alternative boundary for you to use. Alternatively you can always draw your own boundary lines around your area of interest directly in i-Tree Canopy. Our ward boundaries were sourced from: http://geoportal.statistics.gov.uk/datasets/wards-december-2018-full-clipped-boundaries-uk

Ward Status Explained Every ward in the map is given a ‘status’ to help us keep track of the progress of the project. There are three defined ‘status’ each shown in its own colour on the map. Please see the table below for their description.

Example Status Description

Unassigned The ward has not had a canopy assessment completed for it yet. It also has not had anyone come along and ‘assign’ it to themselves to conduct an assessment by downloading the ward boundary to use in the assessment.

Assigned The ward has not had a canopy assessment completed for it yet. However, someone has recently (in the past month) downloaded the ward boundary to complete the ward assessment. So this ward can be considered already ‘in progress’.

Completed This ward has had its canopy assessment completed and the results sent back to Forest Research to be update the map with. The shades of green refer to the level of canopy cover – darker greens indicate a higher level of canopy cover, lighter greens indicate wards with lower levels of canopy cover.





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Tools The web map has a number of tools you can use to get around and edit the map. See the table below for details.

Button Name and Description

About Tool: Click this tool to see more information about the web map with instructions on how to download the ward boundary for a canopy cover assessment.

Editor Tool: Use this tool if you want to download a ward boundary to conduct a canopy cover assessment. Clicking this tool and then the ward you want to work on will bring up a pop-up screen with information on the ward. The ‘Status’ and ‘AssignDate’ fields are editable so you can show this ward is being worked on to others. The ward boundary (a .shp) is listed at the bottom of this pop-up and can be downloaded by clicking it.

Filter Tool: This tool allows you to only show wards of a certain status. For example, if you’re only interested in wards which have completed canopy assessments, you can click this tool and in the first drop-down box select ‘Show completed wards only’.

Find address Tool: Type in a location to zoom to that location on the map.

Home Tool: Click this to return to the original map extent showing the whole of the UK.

Select and download data Tool: This tool allows you to select a set of wards by drawing a rectangle on the map – wards within or overlapping this rectangle are selected. You then have options to review statistics on your selection, or download the data in a number of formats.

Figures The Web map has two figures which show statistics on the progress of the project and average canopy cover levels.


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Figure 1: Shows the proportion of all wards with different statuses. Currently the vast majority of wards are classed as ‘Unassigned’ but we hope as the project goes on to see the proportion of ‘Completed’ wards increase. Hover your mouse over different parts of the diagram to get a pop-up of the number and percentage of wards in the different status levels.

Figure 2: Shows the average canopy cover for wards. This figure will change depending on which wards are visible in the map to the right. For an average for all the UK you’d need to zoom out so that all of the UK is visible in the map view. But remember, this canopy cover average is only counting the wards with completed canopy assessments.


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